The present invention relates to an absorbent article particularly suited for everyday feminine hygiene and for protecting an undergarment against staining from light, daily secretions and discharges. It comprises a very thin, lightweight, highly absorbent pad which is soft, supple and easily conformable to the body and the garment to which it is adhesively attached. More particularly, the article comprises a garment side surface which contains recesses and an adhesive layer which contacts and follows the contours of this surface including the recesses. The present invention further relates to an apparatus and method for manufacturing an absorbent article, which article comprises a garment side surface containing recesses and an adhesive layer which contacts and follows the contours of the garment side surface including the recesses.
The prior art is replete with patents relating to protective pads and shields since the protection of undergarments from staining, especially for the many women who are troubled with frequent, light bodily discharges, has been a long standing problem. These patents generally describe layered structures having a porous body contacting layer overlying a liquid impermeable garment side barrier layer, and a layer of absorbent material between the body contacting layer and the barrier layer. An adhesive is attached to the garment side of the fluid barrier to secure the assembled shield to the crotch portion of an undergarment. And, a release layer is removably affixed to the adhesive layer to keep the adhesive from making contact to anything until it is placed in the undergarment.
As for the materials of construction of the absorbent pad, body-contacting layers of the prior art include absorbent, porous, dry-laid, nonwoven webs or scrim type materials such as those described by I. S. Ness in U.S. Pat. No. 4,880,419 and by Campau in U.S. Pat. No. 3,044,467, Hendricks in U.S. Pat. No. 3,463,154 and Sneider in U.S. Pat. No. 3,570,491. Such materials are often coarse textured and harsh to the touch and, because of their absorbency, wet from the top surface down during use resulting in a constantly moist surface against the skin.
Body-contacting layers of the prior art such as those described by T. J. Luceri in U.S. Pat. No. 4,795,455, by S. Cadieux in European Patent No. 354,502, by A. T. Mays in European Patent No. 70,163, and by R. P. James in U.S. Pat. No. 4,368,323 include nonwovens made from hydrophobic fibers which have been coated with an adhesive or have been subjected to heat and/or pressure to fuse the individual fibers to each other. Such materials tend to have only limited absorption but serve to allow passage to lower layers for absorption and retention. As a result, the fluid is wicked away from the body, leaving the surface of the body-contacting layer feeling dryer to the touch.
The use of hydrophobic fibers for the body contacting layer allows fluid to pass through to the absorbent layer beneath yet will not retain moisture on the surface layer, thus providing greater comfort to the wearer by feeling dry for a longer period of time. The desirability of such a feature has been recognized by Levesque U.S. Pat. No. 3,838,692 who describes a chemical method of providing porosity to hydrophobic materials.
The absorbent layers taught by the prior art usually consists of pulp fluff as described by S. L. Kopolow in U.S. Pat. Nos. 4,552,618 and 4,555,192, by D. C. Holtman in U.S. Pat. Nos. 4,544,596 and 4,536,432, by P. K. Chatterjee in U.S. Pat. No. 4,474,949.
Alternatively, the absorbent layer of the prior art may consist of blends of pulp fluff and synthetic fibers as described by Malaney in U.S. Pat. Nos. 4,756,786 and in 4,684,570. Or, the absorbent layer may be thermoplastic fibers co-formed with pulp fibers.
It is also possible to disperse into the absorbent layer a super absorbent polymer such as those taught by S. Dabi in U.S. Pat. No. 4,494,963, by I. S. Ness in U.S. Pat. No. 4,880,419 and by J. Roller in U.S. Pat. No. 4,443,492.
The liquid impermeable barrier layer, located between the absorbent layer and the garment, is commonly made of polyethylene, polypropylene, or a like material. Such layers are taught in U.S. Pat. No. 4,731,066 by R. Korpman.
Generally, the earlier prior art teaches absorbent pads made of wood pulp fluff that, when properly manufactured to absorb large quantities of fluid, are thick and bulky. Recent developments in the art teach the use of materials such as sphagnum peat moss (such as that taught by Y. Levesque in U.S. Pat. No. 4,507,122) and super absorbent polymers which, pound for pound, absorb much greater quantities of fluid than pulp allowing for the manufacture of much thinner absorbent pads.
The prior art also teaches the application of heat and/or pressure to bind the fibers of the absorbent layer together into densified areas. As fluid makes contact with such densified areas, the fluid tends to wick across the layer, away from the point of fluid introduction. This action helps to inhibit local saturation of the pad which is one cause of pad failure. See, for example, U.S. Pat. No. 4,059,114 to Richards and U.S. Pat. No. 4,886,697 to Perdelwitz et al., both of which are incorporated by reference.
Once fluid has been introduced to the body contacting surface, pad construction is designed to cause the fluid to flow into the absorbent layer and remain there until disposal of the pad. However, the garment side layer of the structure is usually a liquid impermeable barrier layer which, in the event fluid continues to flow through the pad to the garment side, prevents leakage onto the wearer's undergarments.
While such prior art pads undoubtedly function to protect the undergarments to which they are applied, they are deficient in one primary area of performance. They tend to draw fluid toward the lateral and longitudinal edges of the pad, increasing the likelihood of failure by allowing leakage off the pad onto the wearer's clothes.
More recently, absorbent pads have been developed which form fluid barriers, both on the periphery of the pad and internally, to prevent or at least hinder fluid from migrating to the edge of the pad and leaking onto the wearer's undergarments. Such pads are of multi-layer construction and, optimally, contain fusible fibers in each layer. The fluid barriers are formed by thermally fusing all layers of the pad together in the z-direction (herein defined as the direction through the pad from the body side to the garment side); heat and pressure are selectively applied to cause the fusible fibers to melt and flow into the interstitial spaces between the non-melted fibers. By eliminating the capillary space, fluid flow through the fused areas is eliminated or greatly reduced. See, for instance, U.S. Pat. No. 4,886,697 (Perdelwitz, et al.) and U.S. Patent application Ser. No. 07/960,664, entitled "Garment Shield" and assigned to the same assignee as the present invention.
However, the product described above, especially in thin products, causes the outer layers of the pad (both the body side and garment side surfaces) to become compressed at the areas where heat and pressure are applied. This results in a pad where recesses develop. That is, when looking at the pad in cross-section, the outer surfaces of the pad will curve in the z-direction toward the center of the pad. This is not generally a problem on the body side surface of the pad. In fact, many prior art references exist which call for densification of this surface.
On the garment side surface, however, problems can develop if the surface is not planar. Common commercial practice calls for a positioning adhesive to be applied to the garment side surface to keep the pad in place during use. Such adhesives are, typically, applied by a transfer coating process where the adhesive is first applied to release paper. The adhesive side of the release paper is then brought into contact with the garment side surface of the pad. Because the release paper, typically coated with silicone, has a lower release energy the adhesive will preferentially stick to the garment side surface of the pad. Further, the adhesive is chosen to preferentially stick to the garment side surface of the pad during use, so that when the pad is removed from the wearer's undergarments adhesive will not be left on the wearer's clothes. Such products and processes are taught by Balinth in U.S. Pat. No. 4,335,026; Korpman in U.S. Pat. No. 4,554,191; U.S. Pat. No. 4,946,527, assigned to Proctor & Gamble; U.S. Pat. No. 4,615,696, assigned to Kimberly Clark; all herein incorporated by reference.
If, however, the garment side surface contains one or more recesses the adhesive, when transferred from the release paper to the pad, will bridge the gap across the recess and not come into contact with the surfaces which define the recess. As a result, the adhesive at the recess will either be removed when the release paper is removed from the pad or, more likely, will preferentially stick to the wearer's clothes when the pad is removed after use. The present invention solves this problem.
Additionally, in the step of fusing the layers of an absorbent pad together, it has been discovered that small holes (pinholes) will commonly develop in the garment side (barrier) layer. Thus, in forming a fluid barrier to keep fluid from flowing toward the edges of the pad, the chances of failure through the barrier in the z-direction are increased. Thus, in the event pinholes are created in the barrier layer, it is necessary to find a way to keep fluid from flowing through such holes. The present invention solves this problem.